User guide

MS-DMT Guide v1.04
Released 05-30-2014
66
SETTING UP RX AUDIO
Never use the radio speaker out port. Most all HF radios provide a fixed radio line out at 100 mV
rms @ 600 ohms either on a dedicated data modem port, on a separate port and often on the
MIC port connector. Only make use of radio line out for the data modem RX audio. If you radio
does not provide such a port, it is highly recommended that one be added by wiring to the high
side of the radio volume control for a fixed output port regardless of the volume position.
Using Spectrum Lab (http://www.qsl.net/dl4yhf/spectra1.html) with a fresh install, select your
sound device and then setup the Spectrum display by Right Clicking on the top part of the
spectrum as follows:
Below is the fixed 100mv RX audio of an old FT-890 with stock 2.4kHz filter with is IF Shift
adjusted properly, the radio is on a dummy load, S0 on the meter. The fixed 100mv level
requires adjusting your sound device line in level for -80db (with your radio on a dummy load).